1. Field of the Invention
The present invention relates to a ring network and a network relay device. In particular, it relates to a ring network and a network relay device, capable of handling a failure caused.
2. Description of the Related Art
Conventionally, a monitor for constituting a portion of a ring network and monitoring the ring network is known that has a first and a second ring port for constituting the ring network, and which periodically transmits, from the first and the second ring port, a control frame for monitoring a state of the ring network, to determine whether or not the control frame transmitted from the first ring port is received by the second ring, and whether or not the control frame transmitted from the second ring port is received by the first ring, to thereby monitor a state of the ring network.
This monitor can determine whether or not to relay a user frame based on whether the monitor receives the periodically transmitted control frame. It can therefore realize high-speed path switching.
Refer to JP-A-2008-136013, for example.
However, the monitor disclosed by JP-A-2008-136013 causes a logical loop in the event of unidirectional breakage of transmission line in the network.